You should avoid physical fights when necessary, especially if you're not making money off of them. If you absolutely must get into one, then please, please remember: Keep your hands up. Chances are that you won't see Roy Nelson on the street (and there are very few reasons to get into a fight with a trained fighter), but minimizing your chances of getting knocked out cold like Antônio Rodrigo "Big Nog" Nogueira did is definitely a good idea. Look at how Nelson winded up that punch, too. That's a lot of weight to be transferring on to someone's face.